Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0015695 (fatty liver)
 13,941 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Choline-deficiency causes liver cells to die by apoptosis, and it has not been clear whether the effects of choline-deficiency are mediated by methyl-deficiency or by lack of choline moieties. SV40 immortalized CWSV-1 hepatocytes were cultivated in media that were choline-sufficient, choline-deficient, choline-deficient with methyl-donors (betaine or methionine), or choline-deficient with extra folate/vitamin B12. Choline-deficient CWSV-1 hepatocytes were not methyl-deficient as they had increased intracellular S-adenosylmethionine concentrations (132% of control; P < 0.01). Despite increased phosphatidylcholine synthesis via sequential methylation of phosphatidylethanol-amine, choline-deficient hepatocytes had significantly decreased (P < 0.01) intracellular concentrations of choline (20% of control), phosphocholine (6% of control), glycerophosphocholine (15% of control), and phosphatidylcholine (55% of control). Methyl-supplementation in choline-deficiency enhanced intracellular methyl-group availability, but did not correct choline-deficiency induced abnormalities in either choline metabolite or phospholipid content in hepatocytes. Methyl-supplemented, choline-deficient cells died by apoptosis. In a rat study, 2 weeks of a choline deficient diet supplemented with betaine did not prevent the occurrence of fatty liver and the increased DNA strand breakage induced by choline-deficiency. Though dietary supplementation with betaine restored hepatic betaine concentration and increased hepatic S-adenosylmethionine/S-adenosylhomocysteine ratio, it did not correct depleted choline (15% of control), phosphocholine (6% control), or phosphatidylcholine (48% of control) concentrations in deficient livers. These data show that decreased intracellular choline and/or choline metabolite concentrations, and not methyl deficiency, are associated with apoptotic death of hepatocytes.
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PMID:Methyl-group donors cannot prevent apoptotic death of rat hepatocytes induced by choline-deficiency. 902 80

Alcohol-induced tissue damage results from associated nutritional deficiencies as well as some direct toxic effects, which have now been linked to the metabolism of ethanol. The main pathway involves liver alcohol dehydrogenase which catalyzes the oxidation of ethanol to acetaldehyde, with a shift to a more reduced state, and results in metabolic disturbances, such as hyperlactacidemia, acidosis, hyperglycemia, hyperuricemia and fatty liver. More severe toxic manifestations are produced by an accessory pathway, the microsomal ethanol oxidizing system involving an ethanol-inducible cytochrome P450 (2E1). After chronic ethanol consumption, there is a 4- to 10-fold induction of 2E1, associated not only with increased acetaldehyde generation but also with production of oxygen radicals that promote lipid peroxidation. Most importantly, 2E1 activates many xenobiotics to toxic metabolites. These include solvents commonly used in industry, anaesthetic agents, medications such as isoniazid, over the counter analgesics (acetaminophen), illicit drugs (cocaine), chemical carcinogens, and even vitamin A and its precursor beta-carotene. Furthermore, enhanced microsomal degradation of retinoids (together with increased hepatic mobilization) promotes their depletion and associated pathology. Induction of 2E1 also yields increased acetaldehyde generation, with formation of protein adducts, resulting in antibody production, enzyme inactivation, decreased DNA repair, impaired utilization of oxygen, glutathione depletion, free radical-mediated toxicity, lipid peroxidation, and increased collagen synthesis. New therapies include adenosyl-L-methionine which, in baboons, replenishes glutathione, and attenuates mitochondrial lesions. In addition, polyenylphosphatidylcholine (PPC) fully prevents ethanol-induced septal fibrosis and cirrhosis, opposes ethanol-induced hepatic phospholipid depletion, decreased phosphatidylethanolamine methyltransferase activity and activation of hepatic lipocytes, whereas its dilinoleoyl species increases collagenase activity. Current clinical trials with PPC are targeted on susceptible populations, namely heavy drinkers at precirrhotic stages.
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PMID:Ethanol metabolism, cirrhosis and alcoholism. 902 26

Two trials were conducted to examine the effects of supplemental methionine, provided as methionine hydroxy analog 13 g/d), or fat (454 g of calcium salts of long-chain fatty acids/d) on hepatic triglyceride concentration. In the first experiment, methionine hydroxy analog or fat was fed during feed restriction to determine if hepatic triglyceride accumulation is affected. The objective of the second experiment was to determine if feeding fat or methionine hydroxy analog influences the rate of triglyceride depletion from the liver of cows in positive energy balance following the induction of fatty liver by feed restriction. In experiment 1, feeding methionine hydroxy analog decreased plasma glucose, increased plasma nonesterified fatty acids, and had no effect on liver triglyceride. Feeding fat increased plasma nonesterified fatty acids and increased hepatic triglyceride during the 10-d feed restriction period. In experiment 2, feeding fat decreased the rate of triglyceride depletion from liver when cows were allowed to resume ad libitum consumption of feed; methionine hydroxy analog had no effect. Results of these studies indicate that feeding supplemental fat or methionine hydroxy analog at levels tested does not prevent or alleviate fatty liver induced by feed restriction.
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PMID:Effects of fat and methionine hydroxy analog on prevention or alleviation of fatty liver induced by feed restriction. 1062 20

Carcinogenesis may be effected not only through exposure to exogenous stimuli but also by genetic and epigenetic influences derived from endogenous factors. In the latter case, the mechanisms are still largely obscure because of the limited availability of appropriate in vivo experimental models. However, continuous feeding of a diet deficient in choline and methionine is well known to cause hepatocellular carcinomas (HCC) in rats in the absence of any known exogenous carcinogens and can serve as a good research model. A semi-synthetic, choline-deficient, L-amino acid-defined (CDAA) diet, containing practically no choline and low methionine, induces HCC with a background of fatty liver and hepatocyte death, subsequent regeneration and fibrosis resulting in cirrhosis. Using the CDAA diet, we have revealed the participation of oxidative injury to DNA and other subcellular components and of alteration in intrahepatic signal transduction pathways in the mechanisms underlying this rat liver carcinogenesis model. In the present paper, the current understanding of endogenous rat liver carcinogenesis, due to dietary choline deficiency, is reviewed.
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PMID:Endogenous liver carcinogenesis in the rat. 1063 23

The lipid content of hepatocytes is regulated by the integrated activities of cellular enzymes that catalyze lipid uptake, synthesis, oxidation, and export. When "input" of fats into these systems (either because of increased fatty acid delivery, hepatic fatty acid uptake, or fatty acid synthesis) exceeds the capacity for fatty acid oxidation or export (i.e., "output"), then hepatic steatosis occurs. Genetic causes of increased fatty acid input promote excessive hepatic lipogenesis. These include mutations that cause leptin deficiency or leptin receptor inhibition and mutations that induce insulin, insulin-like growth factors, or insulin-responsive transcription factors. Genetic causes of impaired hepatic fatty acid oxidation inhibit the elimination (i.e., output) of fat from the liver. These include mutations that inhibit various components of the peroxisomal and/or mitochondrial pathways for fatty acid beta-oxidation. Environmental factors, such as diets and toxins, can also unbalance hepatic fatty acid synthesis and oxidation. Hepatic lipogenesis is increased by dietary sucrose, fructose, or fats and certain toxins, such as ethanol. Hepatic fatty acid oxidation is inhibited by choline- or methionine-deficient diets and other toxins, such as etomoxir. Animals with genetic or environmental induction of hepatic lipogenesis appear to be useful models for human nonalcoholic fatty liver disease in which hyperinsulinemia and defective leptin signaling are conspicuous at early stages of the disease process.
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PMID:Animal models of steatosis. 1129

Liver-specific and nonliver-specific methionine adenosyltransferases (MATs) are products of two genes, MAT1A and MAT2A, respectively, that catalyze the formation of S-adenosylmethionine (AdoMet), the principal biological methyl donor. Mature liver expresses MAT1A, whereas MAT2A is expressed in extrahepatic tissues and is induced during liver growth and dedifferentiation. To examine the influence of MAT1A on hepatic growth, we studied the effects of a targeted disruption of the murine MAT1A gene. MAT1A mRNA and protein levels were absent in homozygous knockout mice. At 3 months, plasma methionine level increased 776% in knockouts. Hepatic AdoMet and glutathione levels were reduced by 74 and 40%, respectively, whereas S-adenosylhomocysteine, methylthioadenosine, and global DNA methylation were unchanged. The body weight of 3-month-old knockout mice was unchanged from wild-type littermates, but the liver weight was increased 40%. The Affymetrix genechip system and Northern and Western blot analyses were used to analyze differential expression of genes. The expression of many acute phase-response and inflammatory markers, including orosomucoid, amyloid, metallothionein, Fas antigen, and growth-related genes, including early growth response 1 and proliferating cell nuclear antigen, is increased in the knockout animal. At 3 months, knockout mice are more susceptible to choline-deficient diet-induced fatty liver. At 8 months, knockout mice developed spontaneous macrovesicular steatosis and predominantly periportal mononuclear cell infiltration. Thus, absence of MAT1A resulted in a liver that is more susceptible to injury, expresses markers of an acute phase response, and displays increased proliferation.
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PMID:Methionine adenosyltransferase 1A knockout mice are predisposed to liver injury and exhibit increased expression of genes involved in proliferation. 1132 Feb 6

Five patients of cholestatic jaundice and multiple hyperaminoacidemias were uncovered during neonatal mass screening for homocystinuria. All five patients had increased plasma levels of methionine, citrulline, tyrosine, threonine, phenylalanine, lysine and arginine. Compared with those of age-matched cholestatic disease controls, idiopathic neonatal hepatitis (n=9) and biliary atresia (n=14), plasma levels of three amino acids, citrulline, methionine, and threonine, were significantly greater, respectively (P<0.01). Liver biopsies examined in four patients uniformly showed diffuse hepatic fatty liver with micro- and macrovesicular droplets without giant cell transformation. Administration of fat-soluble vitamins and formula milk containing middle-chain triglyceride resulted in normalization of amino acid profiles by 6 weeks after the treatment. All liver function tests normalized by 17 months of age.
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PMID:An undescribed subset of neonatal intrahepatic cholestasis associated with multiple hyperaminoacidemia. 1147 Jun 24

In patients with severe alcoholic liver disease (i.e., cirrhosis), a deficiency of S-adenosylmethionine (SAMe) develops as a result of decreased SAMe synthetase activity. Whether a sizeable SAMe depletion occurs already at earlier stages of alcoholic liver disease has been the subject of debate. To address this issue, rats were fed alcohol (or isocaloric carbohydrate) in Lieber-DeCarli liquid diets containing adequate amounts of protein, vitamins, and lipotropic factors, including methionine. Alcohol feeding resulted in hepatic steatosis (without fibrosis) and unchanged SAMe synthetase activity, yet SAMe concentration was already greatly decreased. This most likely resulted from oxidative stress associated with the metabolism of alcohol and the induction of cytochrome P4502E1 (CYP2E1), which generates free radicals. Indeed, the decrease in hepatic SAMe correlated with parameters of oxidative stress, such as increased 4-hydroxynonenal (measured by gas chromatography-mass spectrometry) and diminished glutathione (GSH). Decreased GSH, occurring as a result of excessive GSH consumption caused by the oxidative stress, probably generated by enhanced utilization of SAMe, a precursor of GSH, thereby explaining the depletion of SAMe. In view of the known differences between rodents and primates in the metabolism of lipotropes, my colleagues and I have also studied the interaction between alcohol and SAMe in baboons and found again that, at early stages preceding the development of cirrhosis, there was already a significant lowering of hepatic SAMe concentration, associated with a striking oxidative stress documented by decreased levels and accelerated turnover of GSH. This was associated with increased lipid peroxidation and damage to cellular membranes, including those of the mitochondria, assessed by electron microscopy. Oral administration of SAMe resulted in its hepatic repletion with a corresponding attenuation of the ethanol-induced oxidative stress and liver injury, with significantly less GSH depletion, less increases in plasma aspartate aminotransferase (AST) levels, less leakage of mitochondrial glutamic dehydrogenase into the plasma, and fewer megamitochondria. In conclusion, (1) both in rodents and in non-human primates, significant SAMe depletion occurs already at early stages of alcoholic liver disease, despite the consumption of adequate diets; (2) the decreased hepatic SAMe concentration and the associated liver lesions, including mitochondrial injury, can be corrected with SAMe supplementation; and (3) accordingly, therapeutic administration of SAMe should be the subject of a comprehensive clinical trial to assess its capacity to attenuate early stages of alcoholic liver injury in human beings.
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PMID:S-Adenosyl-L-methionine and alcoholic liver disease in animal models: implications for early intervention in human beings. 1216 46

Animal models of hepatic steatosis and steatohepatitis have improved our understanding of the pathogenesis of non-alcoholic fatty liver disease (NAFLD). Three models, genetically obese ob/ob mice, lipoatrophic mice and normal rats fed choline-deficient, methionine-restricted diets, have been particularly informative. All support the multiple 'hit' hypothesis for NAFLD pathogenesis that suggests that fatty livers are unusually vulnerable to oxidants and develop steatohepatitis when secondary insults generate sufficient oxidants to cause liver cell death and inflammation. Steatohepatitis, in turn, increases sensitivity to other insults that induce hepatic fibrosis, promoting the evolution of cirrhosis. Early during NAFLD pathogenesis, inhibitor kappa kinase beta (IKKbeta), an enzyme that induces tumour necrosis factor alpha (TNFalpha) and other proinflammatory cytokines, is activated and this causes insulin resistance. Inhibition of IKKbeta or TNFalpha improves insulin sensitivity, steatosis and steatohepatitis in animals, suggesting novel strategies to prevent and treat early NAFLD in humans.
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PMID:Animal models of steatohepatitis. 1240 39

Chronic alcohol consumption may lead to primary and secondary malnutrition. In particular, protein energy malnutrition not only aggravates alcoholic liver disease but also correlates with impaired liver function and increased mortality. Therefore, in these patients, adequate nutritional support should be implemented in order to improve their prognosis. Clinical trials addressing this issue have shown that nutritional therapy either enterally or parenterally improves various aspects of malnutrition, and there is increasing evidence that it may also improve survival. Therefore, malnourished alcoholics should be administered a diet rich in carbohydrate- and protein-derived calories preferentially via the oral or enteral route. Micronutrient deficiencies typically encountered in alcoholics, such as for thiamine and folate, require specific supplementation. Patients with hepatic encephalopathy may be treated with branched-chain amino acids in order to achieve a positive nitrogen balance. Fatty liver represents the early stage of alcoholic liver disease, which is usually reversible with abstinence. Metadoxine appears to improve fatty liver but confirmatory studies are necessary. S-adenosyl-L-methionine may be helpful for patients with severe alcoholic liver damage, since various mechanisms of alcohol-related hepatotoxicity are counteracted with this essential methyl group donor, while a recent large trial showed that the use of polyenylphosphatidylcholine is of limited efficacy.
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PMID:Review article: Nutritional therapy in alcoholic liver disease. 1294 Sep 21


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